This invention relates to the wheel assembly for a cart or other mobile mechanism, of the type which contains a wheel which swivels around a vertical axle, and may be locked or unlocked by the rotation of the latter in one direction or the other. Such wheel assemblies include a thrust bearing with at least one circular housing fixed by axle, a fork joint with at least two lateral extensions whose lower ends support the wheel's horizontal axle, and one upper circular cover connected to the upper ends of the lateral extensions. The cover cooperates with bearings placed around the lower end of the vertical axle so that the fork joint can rotate around the latter. Prior art wheel assemblies are known to contain devices for locking the fork joint in relation to the vertical swivel axle. Such devices are disclosed, for example, in British Patent GB-A-2106-378.
In the device disclosed in the '378 patent, part of the fork joint's locking device is accessible from the outside and may be damaged. Because of this, the proper operation of the device cannot be assured on an ongoing basis. Moreover, the known wheel assembly of this patent requires a major modification to the fork joint, particularly in the area of the wheel axle, which must be capable of moving in the oblong openings made in the fork joint. Another problem with this known swivelling wheel is the fact that controlling the unlocking of the fork joint entails abruptly stopping the wheel for an instant. In addition, the locking devices for the known swivelling wheel assembly have a large number of unprotected individual parts, and are therefore, subject to rapid wear and deterioration.